Minimum Stirrup Spacing - CSA A23.3
Minimum Stirrup Spacing - CSA A23.3
(OP)
I have a 10"x24" concrete grade beam with 10M stirrups @ 14" o/c, 2-20M bars T&B, 1-1/2" clear cover.
My loading includes strong and weak axis shear plus a torsional load, and I need to have the minimum stirrup for capacity and my Tf>0.25Tcr.
According to C11.3.8.1. the max spacing for stirrups is 0.7dv or 600mm, and in C11.3.8.3 if Tf>0.25Tcr, this minimum spacing shall be reduced by 1/2.
My question is which dv do I use? Will it be the shear depth of the weak axis (dv=7.2")? It would make the maximum stirrup spacing allowed to be 2-1/2" o/c which seems overkill. If I use the dv for strong axis (dv=20") the max stirrup would be 7" o/c.
I do require the stirrup reinforcement for the strong axis since the Vf exceeds Vc in strong axis, but my weak axis shear is smaller than Vc for weak axis and won't theoretically require stirrup reinforcement. Should I be using a dv value of between 7.2" and 20" since there's an interaction between the two shear force vectors?
My loading includes strong and weak axis shear plus a torsional load, and I need to have the minimum stirrup for capacity and my Tf>0.25Tcr.
According to C11.3.8.1. the max spacing for stirrups is 0.7dv or 600mm, and in C11.3.8.3 if Tf>0.25Tcr, this minimum spacing shall be reduced by 1/2.
My question is which dv do I use? Will it be the shear depth of the weak axis (dv=7.2")? It would make the maximum stirrup spacing allowed to be 2-1/2" o/c which seems overkill. If I use the dv for strong axis (dv=20") the max stirrup would be 7" o/c.
I do require the stirrup reinforcement for the strong axis since the Vf exceeds Vc in strong axis, but my weak axis shear is smaller than Vc for weak axis and won't theoretically require stirrup reinforcement. Should I be using a dv value of between 7.2" and 20" since there's an interaction between the two shear force vectors?
RE: Minimum Stirrup Spacing - CSA A23.3
RE: Minimum Stirrup Spacing - CSA A23.3
The grade beam is supporting a pre-eng moment frame column and the vertical and horizontal reactions are quite high ~250kN gravity and ~150kN horizontal kickout. The torsion comes from a 9.5" eccentricity due to the fact that they offset the grade beam with the centre of the columns using a corbel. The column is anchored with 2-25M hairpin reinforcement into a 6" slab-on-grade to resist the kickout force but not all of the lateral force are transferred to the hairpins and some go into the grade beam and piles.
RE: Minimum Stirrup Spacing - CSA A23.3
RE: Minimum Stirrup Spacing - CSA A23.3
Why are you mixing your units? kN and " don't belong in the same sentence.
RE: Minimum Stirrup Spacing - CSA A23.3
As of now, if all the lateral force transfers to the hairpins (which is how it was probably designed to cancel the reactions from the other side of the frame), the grade beams will be over-utilized in torsion due to the eccentricity of the gravity loads alone.
But, if some of the lateral force gets transferred to the piles, the applied torque on the grade beams actually gets reduced since the resultant torque from the kickout force on top of the grade beam counteracts the torque from the eccentric gravity load, but there will be weak axis bending & shear in the grade beam. Hence, I wanted to check the grade beam if it passes capacity and code requirements with this configuration.
RE: Minimum Stirrup Spacing - CSA A23.3
I also have it so that there are lateral supports on top of the grade beam from the 6" slab-on-grade, so if the grade beam ever tries to torsionally rotate it would lean on the slab-on-grade at some point. This probably would be questionable as well since there's a 1/2" bond breaker b/w the slab and the grade beam but I'm doing it for the benefit of the SEOR.
As for the units, my university thought me using mostly metric but at work we usually use imperial in our drawings. My stress/force calcs are always in metric and I always convert imperial dimensions to metric to do my calcs. The imperial dimensions are just easier for me to visualize since my previous job involve building pre-eng trusses in imperial units. You are right though, they should never appear in the same sentence and I'm working on being consistent with one unit system to avoid potential errors.
RE: Minimum Stirrup Spacing - CSA A23.3
Perhaps a sketch would help to understand the grade column/beam/corbel/pile connection.
RE: Minimum Stirrup Spacing - CSA A23.3